Combustor sectional liner structure with annular inlet nozzles



Jan. 18, 1955 D. c. BERKEY 2,699,648 COMBUSTOR SECTIONAL. LINERSTRUCTURE WITH ANNULAR INLET NOZZLES Filed Oct. 3. 1950 2 Sheets-Sheet lInventor: Donald C. Berkey, by

I i mur His AttOrhey.

N h mw mw m r W QE MN mm h m- I I I v? w m Jan. 18, 1955 D. c. BERKEY2,699,648

COMBUSTOR SECTIONAL LINER STRUCTURE WITH ANNULAR INLET NOZZLES FiledOct. :5. 1950 2 Sheets-Sheet 2 Fig. 5.

Va VZJQNW/M I I/ Z4 4 Zla a! 23 2 inventor:

His Attorney.

United States Patent COMBUSTOR SECTIONAL LINER STRUCTURE WITH A'NNULAR'INLET NGZZ'LES .Donald -C. Berkey, Scotia, N. Y., assignor to GeneralElectric Company, a corporation of New York Application October '3,1-950, Serial 'No. 188,153

6 Claims. ((31. 60--.-39.65)

This invention relates to combustion chambers or combustors for burning'fluid fuel 'under pressure, as in 'a gas turbine powerplant,particularly to a special louver structure for admitting 'a cooling andinsulating sheath of pure a'ir along the inner surface of "the linerdefining the combustion space.

The invention is particularly applicable to combustors of the so-calledNerad type disclosed in the United States Patent 2,601,000.0f Anthony J.Nerad, issued-June 17, 1952, .on an applicationSerialNo. 750,015, filedMay 23, 1947, and assigned to the sameassigneeas the presentapplication. The specific gastturbine corribustorfor which the presentinvention was developed'is .disclosed inUnited StatesPatent 2,547,619issued April 3, 195.1, on an "application of 'B. "O. Buckland, SerialNo. 621333, filed November 27, 1948, and assigned to the same assignee.This .combustor comprises a substantiallycylindricaliouter housing anddisposed thereina cylindrical 'liner structure spaced from the outerhousl'mgto define .an annulara'ir 'supply passage communicating .withlongitudinal'rows'of circular combustion air in'letports. The {linerassembly comprises a dome member closing one end and -a pinrality ofseparate circular :sections having-adjacent -end portionsarranged inconcentricradially spacedrelationto definea series or annularznozzlesforinjectingairto' form a cooling and insulating sheath along the innersurface .of'the nextsucceedingsection. 'Thus, the entire inner-surfaceof the liner is kept comparatively free "from "contact withpartly burnedcarbon particles intthe combustion space. This arrangement .has been.foundparticu- "larly effective in preventing the deposition 'of carbonon the liner wall, with the resulting .tendency to produce fhot 'spotsand the accompanying tendency for the linerto buckle or burn through.Inxorderto obtain longZlife-for *the'liner andreduee or eliminatethe-deposition of carbon 'so that only infrequent inspection andcleaning is required, it has been found advisable to very carefullycontrol the velocity of air through the annular :supply 'spacesurrounding the liner, particularly to achieve a 'uniformcooling effectby providingconstant velocity-flow of air in this annular space. that"thevelocity and radial thickness o'f the sheath ;of cooling andinsulating air projected along the inner 'sur- Ffaces of the liner=sections:must be carefully selected if *this protective sheath is to:per'formits intended function effectively.

Accordingly, an object of the ,present invention is ,to

It "'has also been learned 2,699,648 Patented Jan. 18, 1955 g 2insulatingair, 'Fig. 4 is a partial sectional view of a somewhatmodified "form of the special louver arrangement, :and Figs. '5, 6 and 7are diagrammatic illustrations of the method of operation of the louverstructures.

Generally, the objects of the present invention are at- .tained bygiving 1116'll1161 sections such a shape as to prowide :a smoothly andcontinuously contracting area for the mil-supply 'space defined betweenthe liner and the outer zLllDllSlIlgfSOthitilhC air velocity thereinwill be maintained iava'wery'rnearly constant'value of the magnituderequired ffior most zetfective cooling of the outersurrace of the linersanctions. The downstream end of each liner section is provided with anannular louver-defining portion including a radia'lly inwardly extendingwall portion adapted atozcooperatewith the adjacent edge of the nextsucceediingil'iner section to form a substantially sharp-edged inlet:orifice,:and'an axially extending portion adapted to overlaptthe innersurface of the next adjacent liner section and radially spaced therefromto define the cooling and :insulatingsheath discharge orifice. Thisspecial louvercdefining section gar-the downstream end of-each linersegimentihascatspecial advantage inthat it provides a stiffening effectfor -therrespective liner sections, helping them itowresistithermaldistortion which might otherwise change tthe :shape and :effective areaof the annular cooling air nozzles.

Referring-now more particularly to Fig. 1, the comcbustor :is:illustrated as comprising an outer housing 1 definingzahoneend an:inlet passage .2 for receiving air .Ufldfil' pressure sfrom'a suitablecompressor (not shown). .llhe eliner which serves to define thecombustion space :PEQPBI :comprises 'aplurality of sections indicatedgen- .erally-at-G, '4, 5,6, and 7. The initialsection 3 is the tendidomeiassem'bly comprising an inner domerS sur- .-rounded by a :spaeedsubstantially hemispherical shroud 8; =Fhis-end dome-and shroud assemblyare as disclosed in the abovermentioned Patent 2,547,619 of 13.0.Buckland ,andmeed -not be described -in detail here, exceptstoanoterthat air from=the-inlet passage 2 passes through to. @lurality:of metering holes 10, diffuses uniformly throughithe air supply spacedefined betweenidome -8 and 23h0l1d59 and enters the primary combustionspace of =the.-liner-.through arplurality of-ports *11 having associatedstherewithrdefleeting plates 12 arranged -to direct :a thin film ofcooling and insulating'air radially inward toward -:the fuel noz'zle1-3. The outer circumferential portion of :dome- 8ris iradially -spacedfrom the innersurface of liner zseetion mtoidefinean annular nozzlethrough which coolriugzand tinsulatingcair flows along the innersurfaceof .aseetion4, as :indicated by the arrow 4a: in Fig. 1. The endd0me;:per--se-'isof the general type disclosed in Patent 2,581,999,,issued January *8, 19-52, of Walter L. Blatz, ;assigned to the "sameassignee.

il hetfirst cylindrical liner section 4 is secured, as by welding, ltothe adjacent edge-of the domeshroud 3, and is presided with sixcircumferentially spaced air inlet ports -;14,, "the spacing andarrangement of which are in accordance with the above identifiedapplication of :Arlthonyd. =Nerad. This initial liner section may alsowrbemrovided with a-hole for admitting the end portion 'providejanimproved liner structure in combination with "an outerhous'ingso'arranged that unifonmcooling of" the outer surface of the liner iseffected by reason of "the constant velocity air :fiow provided "in "theannular air suprilyspace between liner and housing.

-Another object is to provide :an improved louver arran'gement forforming the cooling and insulating sheath tof air ou 1 the innersurfaces of Ithe zliner.

:A still :further object is "to 1 provide a liner :of the ssectionaltype with specialustiifening :means for preventing thermal distortion ofthe respective tlineri sections.

Other objects and advantages will 'become apparent from the ,followingdescription, taken, in :connection with theaccompanyingdrawings inwhichliig. 1 is,a,,partial sectional assembly viewo'f a, gas turbinecombustor having a.liner inaccordance with the invention,IFi g. 12;is

a detail view in elevation showing the meansfor supporting:a'djacent"end portions of the liner sections relative to teach "other,Fig. 3 is 'an "enlargedzsectional view of are special =louver structurefor admitting thex coo'lingand qofaa suitable spark plug for ignition,and a port com- ..municating with a cross ignition tube for communicat-,,ing. flame:from one combustor-to another. These openiingsaare notillustrated in Fig. 1 because not material atoaniunderstanding of thepresent invention.

Ehe,second-. cylindrical liner section S has three circumferentialrowsof air inlet ports 14 and is supported adjarcent-sitstdownstream endby'means of a plurality of re- -,silient .brackets or loops indicatedgenerally at -15, the ,precise structure-of .which is disclosed morefully in the above-mentioned patent of B. O. Buckland. It need only,bemotedhere ,thatthese supports 15 are intended to ac--euratelyimaintain thesection Sconcentric withthe outer ihollsingilwhile permittingsome differential thermalexpansionitherebetween withoutimposing excessive stresses on the ,respective parts. The ,left iand endportion of section-'5 is supported in coaxial relation with the adja-;cent:;end of section 4 by means of a plurality of axially extendinykeymembersqcomprising a bracket 16 secured,

so as by spot welding at 16b (Fig. 2), to the outersurface o'fthessection {,4 and having an axially extending finger l the elements16, 17 described above.

brackets welded to the outer surface of liner .SQClIiOnnS.

These brackets are shown at 17 in Figs. land 2;.and

comprise one leg 17a spot-welded, as at 17c, to the. outer .rcircumference of liner section 5 and a radially projecting .leg 17badapted to slidingly engage the side surfaces of the finger portion 16a.It will be appreciated of course that there are three .or more of thesepositioning devices disclosed in the above-described patent of B; O.Buckland,

and the detailsneed not be described further here.

Similarly, the liner section 6 is supported by resilient brackets (notshown) similar to those shownat 15 in Fig. .1, and by a finger-keywayconnection 18 similar to Liner section 6 also has three circumferentialrows of air inlet ports 14 arranged similarly to those shown in section5.

' for holding adjacent ends of the liner sectionscoaxiahili Thissupporting arrangement is generally similar to that Liner section 7 islikewise supported by resilient brackets i'. II

19 and finger-keyway members indicated generally at 20.

. It will be apparent from Fig. 1 that the combustion air inlet ports 14in the respective liner sections 4, 5. 6 are arranged in strai htlongitudinal rows that admit the air required both for the combustionprocess and forif' cooling and diluting the hot gases to a temperaturewhich the gas turbine rotor can stand. The function of the cooling andinsulating air indicated by the flow arrow-4a in Fig. l, and the similarannular iets defined by the special nish combustion air but to provide acooling effect for the liner wall and. more important. to provide aprotective louver arran ement described hereinafter. is not to fur-K Iblanket of substan i lly pure a r alon the inner surface of e the linerwall so that partly burned fuel particles in'the combustion space willnot contact the comparatively cool liner and be deposi ed thereon ascarbon. reouiring frequent inspection and cleaning of the combustor.

. The special louver arran ement for providing these cooling and insulting air s eaths c mprises an annular cated. for instance. by rollin barst ck to a ring shape, machini it to the cross-section indica d. andWelding to the adi cent end of liner section 4. The cross-section comustor and havin a d meter (I iden ified specifically section shown inFitz. 1 at 21 as being separately fabriin Fi s. 1 and 3 s 1. 1 Thissmooth surfa e terminates. j,

. at a shar machined sonare corner 210, from which the surface 21!)extends radially in ard and then curves smoothl in to a ener lly axi ldirection to merge with the axially extending substantially cylindricalsurface 211:.

The inner surface of ring 21 curves smo thly so as to" join the innersurface of liner section 4 at 21d and tapers outwardly at 21s to form acomparatively narrow terminal ed e 21f. i

The next adiacent liner section 5 is spaced axiallvfrom the ring 21 soas to defi e an annular inlet opening 23 having an axi l width indicatedw in Fig. 3 and aradial "height indicated h. It is also to be noted thatthe surface 21c pro ects int the liner section 5 with an overlap of a manitude indicated by the dimension 0. It remains to be observed that theed e of liner section 5 adiacent'g:

- the annular in et is beveled as indicated at 22 in Fig. 3,

for a reason which will become apparent hereafter.

The proper magnitude for the critical dimensions of this special louver,and the significance of the shape and dimensions, will become apparentfrom the following de scription of the method of operation. 7 Throughoutthis description of the operation, it is to i be noted that everyattempt is made to prevent the velocity head in the passage 2a havingany effect on the rate of flow through the cooling and insulating louvernozzles 23, 24. In the normal operation of the Nerad type combustor,there will be a static pressure difference 'on the order of 1 to 3% ofthe initial pressure between the air Q supply space 2a and thecombustion spacewithin the, liner. It is, of course, this pressure dropwhichcauses the 'flow'of combustion air inwardly through the ports 2a bemaintained constant.

mode of operation of the Nerad combustor. In order to keep the velocityof the annular cooling and insulating air jets as low as possible, thewhole design of louvers in accordance with this invention is arranged sothat only this static pressure difference produces the flow through thelouvers, no increment being added thereto by any conversion of velocityhead to static head.

As will be appreciated by those skilled in the art of gas turbinedesign, the compressor and related passages which supply air to thecombustion system are' very carefully designed so that the supply isuniform in pressure, velocity, and direction. Thus it is assumed thatthe flow into the combustion chamber through the inlet 2 is perfectlyuniform so that air is supplied at uniform pressure and velocity throughthe annular supply passage 2a defined between the liner assembly and theouter housing 1. It will also be appreciated that it is desirable thatthe velocity of the air flow in passage 2a be so selected as to give theoptimum cooling effect for the liner walls. In the combustor for whichthe present invention was developed, this optimum velocity was found tobe on the order of 260 feet per second, with a compressor dischargepressure on the order of lbs. per square inch, absolute. In other words,the axial velocity headof the air flow in the annular passage 2arepresents on the order of 2% of the total head of the air supplied tothe combustor. In

order to maintain the velocity constant at this optimum value along thelength of the air supply passage 2a, the succeeding liner sections 4, 5,6, 7, taper progressively outward so that the effective area of thepassage 2a progressively decreases as more and more of the air flowsinto the combustion space through the air supply ports 14 and thesuccessive louver inlets 23. It will be seen in Fig. 1 that the firstliner section 4 is a right circular cylinder, having an outer surfaceparallel with the inner surface of the housing 1. However, since acertain amount of the'air in passage 2a enters the combustion spacethrough the first row of holes 14 in liner 4, and a further incremententers through the annular inlet 23, it is necessary that the linersection 5 be of a somewhat greater outside diameter in order that theaxial velocity in passage Specifically, it will be seen that thediameter d2 of the left-hand end of liner section 5 is appreciablygreater than the diameter d1 of the adjacent end of liner section 4.Furthermore, linersection 5 is not a right circular cylinder but flaresgradually outward to a still larger diameter d3 at the right-hand endthereof. Similarly, the diameter d4 of the left-hand end of linersection 6 is still greater than the diameter ds, and section 6 flaresoutward to an even greater diameter 115.; Since the ouantityof airflowing through the last annular louver 23b is comparatively small, andsince the cooling requirements for the last liner section 7 are not so.severe, by reason of the fact that combustion air entering through thesucceeding ports 14 has effected considerable dilution and cooling ofthe combustion gases, the diameter d6 of liner 7 may be madesubstantially or exactly equal to the diameter d5 of the adjacent edgeof liner 6.

Asa general guide, it may be observed that the effective area of thesupply space 2a decreases about 20% along the length of section 5.

The function of the beveled upstream-liner edge portion 22 (Figure 3)will be seen from the following. Assume first that this beveled portionwas omitted and the upstream edge of liner section 5 had a blunt leadingedge 5a disposed normal to the approaching velocity V0,

as shown in Figure 5. This high velocity flow will tend to separatecleanly'from the sharp corner 21a and impact directly on the normalsurface 5a. The result will be that the approach velocity V0 will beconverted into oppositely directed transverse velocity components,represented by the arrows V1 and V2.

It will be apparent that the normal surface 5a thus forms a baflle orscoop? serving to direct a portion of the approaching flow V0 into. thelouver, as represented by velocity vector V2. Furthermore, the impactingof the velocity V0 on the blunt surface So will tend to form I somethingof a' stagnation area in which the static pressure is slightlyincreased. This increased static pressure at the inlet 23, taken inconnection with the velocity directing-effect of the surface 5a actingas a baffle, tends to substantially increase the flow through thelouver.

This is undesirable, since every attempt is made in this design toreduce the flow throughthe louver'in order that the spouting velocityfrom the discharge orifice 24 be comparatively low, perhaps on the orderof 190 to 260 ft. per second, as compared with a spouting velocity of p300 to 400 ft. per second which would be produced if some of thevelocity head V in the supply space were converted to velocity V2 intothe louver inlet. The beveled end surface 22 serves to prevent thisincrease of flow into inlet 23, and at the same time serves to make theaxial flow through the passage 2a more smooth and uniform. Since thediameter d4 of liner section is greater than the diameter d3, a similarbevel is provided at the louver entrance 23a. On the other hand, sincethe diameter d6 of liner section 7 is equal to the diameter d5, thebevel is omitted and liner section 7 has a perfectly square blunt endsection.

It will now be seen that each annular inlet opening 23 is in effect, byreason of the sharp corner 21a in combination with the sharp edge of thetapered portion 22, a sharp-edged orifice and that the high axialvelocity of the fluid in passage 2a will tend to carry the fluid pastthis sharp-edged orifice with no tendency for the velocity head V0 inthe passage 2a to be converted into the vector V2, with a resultingincrease in the flow of air into the cooling louver. i The design of thedischarge orifice 24 of each cooling louver is predicated on the theory,which has been confirmed by tests, that a comparatively lower velocityet of a large cross section area has better penetrating power than ahigher velocity jet of smaller size and the same mass flow. It has beendiscovered that the penetrating power of a jet is a function of itscross section area, since it is the tearing effect of the surroundingatmosphere on the stream which eventually breaks up the et. In thepresent case, the annular jet issuing from the orifice 24 is bounded onone side by the inner surface of the next adjacent liner section, sothat only the inner surface of the annular jet is subject to thedeteriorating effect of the turbulent gases inside the liner. Thus theannular jet from the orifice 24 will persist farther than would be thecase if it were subject on both sides to disturbance by a surroundinggaseous atmosphere.

Accordingly, in order to provide a et of goodpenetrating power, theorifice 24 is made of a radial width h of greater magnitude than hashitherto been employed in cornbustors of this type. Of course, otherfactors impose an upper limit on the size of this orifice, particularlythe effect of too great a flow of cooling and insulating air on thetemperature distribution of the hot gases supplied to the turbine. Ifthe annular orifice 24 is too big, then there will be produced anexcessively cool stratum of gas next to the inner surface of the liner,and this stratification may persist throughout the length of the linerso as to show up as non-uniform distribution of temperature at the linerexit. This has a deleterious effect on turbine rotor life and thereforemust be avoided. In practicing this invention, it has been found thatthe radial width h of the annular orifice 24 must .be on the order of l/2% of the diameter of the liner.

The size of the annular inlet 23 to the cool ng louver'is determined bythe consideration that it is desrredthat the major part of the totalstatic pressure drop across the louver should occur at the dischargeportion 24 rather than at the inlet portion 23. If the major portion ofthis pressure drop occurred at the entrance 23, then the resulting highvelocity flow into the louver would be rnore difficult to direct into asmooth axial jet along the inner surface of the next liner section. Itis much easier to produce the required uniformity of the cooling airsheath if the velocity through the entrance 23 is comparatively low andthis air is accelerated at the discharge orifice 24. Accordingly, it hasbeent'ound that the effective area of the inlet 23 should besubstantially larger than the discharge orifice 24, the axial width w ofthe inlet 23 being.

on the order of two times the radial height h of the dis-' chargeorifice 24. I

. This will be understood better by reference to Figures 6 and 7, Assumefirst that the liner sections 4, in Figure 6 are spaced axially todefine a comparatively smaller annular inlet 23a while the annulardischarge orifice 24a is larger than the inlet. Assuming now a ve-.locity in passage 2a as represented by velocity vector .Vo, thestreamlines representing the flow through the inlet 23a would besomething as represented by the broken u flow lines 31, f2.'."'It willbe readily apparent that here medium for the liner.

it is the louver inlet 23a which presents a substantial restriction tothe flow of fluid and therefore determines the fluid quantity flowingthrough the louver. The flow coefficient of inlet 23a would be ratherpoor, since its effective area could be represented as the cross-sectionarea of the flow through the inlet 23a, measured in a direction normalto the average velocity V4 therethrough. This effective area might, forinstance, be represented by the dimension identified A1 in Figure 6. Itis to be noted that the flow line 11 breaks sharply away from the innersurface of liner section 5 so that the stream represented 12) f1, f2does not completely fill the discharge nozzle On the other hand, withapplicants arrangement, the flow is as represented in Figure 7. Here thecontrolling restriction of the quantity flow through the louver is thesmaller area opening at 24b, the inlet 23b being so much larger as topresent little restriction to flow into the louver. Here it will be seenthat the flow line f3 still separates slightly from the inner surface ofliner section 5, as indicated at f4, but the fact that the major portionof the pressure drop occurs at the nozzle 24b insures that the flow willcompletely fill the nozzle. The other flow line f5 breaks sharply awayfrom the square corner 21a.

With this arrangement, the average velocity inwardly through the largeinlet 23]) is comparatively low, because the quantity flowing isdetermined by the flow restriction presented by the comparativelysmaller nozzle 24b, and this quantity of fluid flows through thecomparatively larger inlet 23b. This is the inverse of the arrangementin Figure 6, in which the higher velocity occurs at the inlet 23a, withthe result that the velocity will tend to be lower at the discharge ofthe annular nozzle 21, as indicated by vector Vs. It will be apparentthat the higher axial velocity represented by jet V3 in Figure 7 isdirectly effective to produce the cooling and insulating effect desiredon liner 5, while with the arrangement in Figure 6 the sheathing andcooling effect depends on the conversion of the velocity V4 (which has asubstantialfradial component) into an effective axial jet at V5. Thedirection of the velocity V5 will obviously be much harder to controlthan with the arrangement in Figure 7, where the flow restriction occursat 24b with the desired velocity V3 being produced directly.

It. is also important to the uniformity of the annular jet produced thatthe overlap 0 be of a magnitude on the order of one to two times theradial height h of the orifice 24. This is necessary in order that thefluid flowing radially through the orifice 23 may be directed into theaxial direction and smoothed out to form a uniform annular jet.

It may be noted further that the overall static pressure drop from theinlet 23 to the exit 24 is desired to be on the order of 1% of theinitial total head of the fluid in the supply passage 2a, this factorhaving an additional effect on the magnitude of the discharge orifice24.

The fact that thelouver ring 21 projects radially inward a small amountinto the combustion space does not seem to have any adverse effect onthe flow of hot gases in the liner. As a matter of fact, the smoothlyinwardly curved portion 21d seems to serve the beneficial function ofreceiving any remnant of the insulating air sheath produced by thepreceding annular orifice and directing this air with a radial componentso as to mix it with the hot gases in the combustion space. It will, ofcourse, be appreciated that by the time the insulating sheath of airfrom the preceding annular nozzle reaches this curved surface 21d itwill have picked up considerable heat by contact with the inner surfaceof the liner as well as by radiation from the flame within thecombustion space, so that it is too warm to properly serve as a coolingAt the same time this remnant of the insulating sheath is 'suflicientlylower in temperature than the average temperature of the combustiongases that it is necessary to mix it thoroughly with the hot gases inorder to promote uniformity of temperature distribution. The smoothinwardly curved portion 21d of the louver ring 21 performs thisfunction.

It will be apparent from Figs. 1 and 3 that thecross section of ring 21is comparatively substantial, so that the r ng has an importantstiffening effect tending to hold the liner section to its true circularshape. This is im- 7 4 :ibecause: anyrdistortionrwouldg of course,:alter theethicknessranduniformity? mm airwsheathsn The outward taper2112 atwthewterminal-portion of-the inner a surface ofsthmring' 2-1isiintended toprovide a terminal his :is. importantnsince, a'bluntterminal edge of zsubstantialqradial:width is-permitted, there:will be r; turbulent ieddies produced in.-.the.2wake of: this blunt disachargeedge; ;and ,;such :e'ddies have: an :cxtremely. serious effectinadisturbingcthe-smooth surface of=-the jet issuing from-:the: cooling:louver." For this I reason, the discharge ;21f ismade as narrowaspossible consistent with a ithermechanical strengthqrequired.

With a liner structure having the mechanicaland-aerosdynamicvfeaturesxdescri-bed above, it is found, thateffectivexcooling of; the. liner sections is :provided,:Withopimumvfreedomwfrompcarbondeposition on the interior urfaces.thereof, atogether with long "life and rfr'eedom rom-ethe; necessityofw frequent inspection to safeguard gainst;excessivelocalcarbondeposits, with the resulting 0t. spots :and risk of mechanical failure.

It will of course; be appreciated by those skilled in the rtvthat :gagreat-manyfsmall changes might be made in he mechanicahdesign oftheparts'; For-instance; instead of hQ'r epar-ately-fabricatedmachined.,ring: 21- forming the cooling and insulating louver, this section may.be *forrnejd byzibeing rolled integralrwith the end of the liner ection;as suggested in;;Fig. 4...-Hcre the :corner 21g can- Oebe-madequite assharp as'iwith the separately ma- .--'.gchined arrangement of ;Figs.l'and 3,-but by a' care'ful @.-"rolling =operation; 'thispcorner may bemade to take a -comparatively small radius curvegwithsubstantiallysimilar; results tothose obtained with the structuredescribed above ?Otherwisethearrangement of Fig. 4 is identical a;to-:that described above.

Itgwillwalsorbe apparent that this-*special louver ar- .-z;r angem'cntis applicable toannular combustors having a .tzcombustion spacc which isannular rather than circular as {disclosed herein. Inv such a"combustor; the liner m-wbuld consist; of a-series ofcoaxial radiallyspaced seciv tions having theirp adjacent edge portions forming :the

pjecial' louvers- .:des'cribed above.

Many::other modificationswill be apparent to those a skilled inthe art;andit isdesired to cover by the appended .':claims; a-ll suchi chan'gesas .fallp-within-the true spirit and scope of myinvention.

-What II claim as new and desire to'secure by:Letters f-Patentl of the-1United States is:

1;.- In acombustor having an'outer'housing containaging a; linerdefining :anaxially elongated combustion a -chamber:substantially closedat oneend and-formed of separate wallv sections divided on planes.normal to the axis of the combustion chamber and supported intspaced-irelationto-the outer-housingto define 'a' combustion air upply;passage ;the rebetween, with means for supplying under pressure to said.passagewith a high velocity atoward the dischargeend of; the liner; :thecombination of aqgfirs liner'. section having a-discharge end portioncooperating-with.:.the jadjac'entsupstreamiend: portion of enexttlinensectionto. form an annularnozzle forprogectjng a sheathfi of-cooling. and insulating. fluid along eyinner' surface of said; nextadjacent section :toward the discharge. end thereof; rsaidcdischarge endportion of theiifirst section'having a smooth; outer surfaeetterminatmgati-aisubstantiallysharp annular corner, a second'pornion projectinginwardly and having a substantially radial surface extending inwardlyfrom said sharp corner, and atthird'por-tion extending axially andprojecting in spaced l .para1le1. relation.withand overlapping the innersurface #1. ofthe SCGOHdEliHCI'SBCIiQI] to form said annular sheathinghair- 110 2216, saida-first, second, and third portions of thefirstliner-section cooperating to define 1a smoothly curved incur-facefor treceiving'air;radially and :then turning it rgsmoothl-yfinto anaxial direction and dischargingthrough -;s aid nozzletoward the:discharge end of the :second' liner :vsectioln..the aadjacent. edge ofthe secondliner section being-aspaced:axially fromqsaidysharp cornertozdefine an; annularainlet opening for thesheathing air nozzle, i--whereby fluid,flowing, at ;high axial velocity inthe air supplyspacedbetween' liner=and housing toward the dis- ;nchargeiend'sthereofis caused topflow through; the sheath- -fluidunozzle, by -reason of.:the static pressure: differencesbetwcen thepair; supply andwztheLCOmbUStiOH space ....-pressure;within;;he; iner. 1. 2. A combustorliner structure in accordance with lairntl.in zwhicbzthearadialspacing-:h ofithe overlapping .nozzletporticrnrfrom the inner; surfaceof. theunext -adcent liner sectionz'is on the order of 1 /2% ofzthetransaverse spacing d bet-weeniopposite liner wall port-ions, .theoverlap o by:which *thelouver-defining-nozzle portion'projects?infoatheanext adjacent liner section is on -the :order of -ltor-.2 times h, and theaxial'width-w of the nozzle inlet opening-is: onthe1order of 2 times h.

3 In a" generally. cylindrical combustor' fornburning 10:. fluid-fuelsofrthexype'. having an outerhousing containving anaxiallyrelonga'ted'liner substantially closed at one '1 .enddefining-the-combustion space proper and formed of :scparateannularsectionsisupported coaxially within asy-the outerhousing'andsp'acedtherefrom to define anannular'zcombustionair-,supplyipassage therebetween, with means forsupplying air under-pressure to said passage 1 .with-az high,axial::velocity-toward the discharge end of the liner,:the combinationof a first substantially cylindricalsliner section having a reduceddiaineterdischarge 0 endxportion projecting-into the adjacentupstreamend portion of the, next liner section to define an annular""nozzleforprojecting a sheath of cooling and insulating fluid :alongthe inner surface of said next adjacentsecrtionetowardw the idis'chargeend-thereof, said discharge end portion of the first section having asmooth/outer "surface:terminating at a louver-defining ring vincludinga;first ring portion defining asubstantially sharpannular corner, ascconduring-portion projecting inwardly and forming a'substantiallyradial annular surface extending inwardlyfrom-said sharp corner, and athird ring portion extending axially and projecting in coaxialrelationinto 1 and spacedradiallyfrom the inner surface of the secondvliner'section to form saidannularnozzle for the cooling-,-and-insulating fluid, said first, second, and third portions ofthelouver-defining ring cooperating to define a smoothly' curved surfacefor receiving air radially and then turning it smoothly into an axialdirection and discharging 'throughasaid-annular nozzle -toward thedischarge .end ofwthe-i-second liner section, "whereby-fluid flowing at40 high axial velocity in the air supply passage between liner andhousing toward the dischargeend thereof is caused to flow throughtheannular louver by the static pressure drop from-the'air supplypassage to the combustion 1 space. 4-. A lcombustor liner in accordancewith claim 3 in which the .radial height h of theannular nozzle is on-the'order of 1 /2 of the diameter d of the liner section, the-axialoverlap 0 by which the louver-defining ring-pro- -jects into thenextadjacentliner section is on the order ofone to -twov times h,:and theaxial width of-the louver inlet openingdefined between the sharp annularcorner band the adjacent edge of the second liner section is on theorder oftwotimes h, the inner surface of said louverdefining ring-beingcurved at its upstream side to form a smooth continuation of the innersurface of thefirst .linersection and (the downstream portion ofthetlouverdgfining ring being tapered to a narrow annular discharge wege. t

5. In a cylindrical .fluidfuel. .combustor. of the type corhaving anouter housing containing an axially elongated lincr 'definingthe-combustion space and formed of sep- .arateannulansections supportedcoaxially within, the outer housing and spaced therefrom to define anannular'combustion air supplypassage therebetween withmeans for,supplyingairunder pressure thereto athigh axial velocity toward thedischarge end of the liner, thecomb,ination of a-first substantiallycylindrical liner section-having-a discharge-end portion projecting intothe adjacent :upstreamlnd portionof the next liner section to define anannular nozzle. for projecting a sheath of cooling and. insulating fluidalong the inner surface of said next Ladjacent/section,-said dischargeend portion'having a smooth outer surface terminating at alouver-defining 'ring .including a first ring portion. defining asubstantially sharp annular corner, a second ring portion projectinginwardly and forming a substantially radial annular surface extendinginwardly fromsaid sharp corner, and a third ring portion extendingaxially and projecting in coaxial relation-into and spaced radially adistance h i'fromj-the'innersurface of the second liner'section toform-"said annular nozzle for the cooling and insulating fiuid, saidvdimension hbeing on the order of 1 /2% of=the .diameter Of-the-Iinersection, said first, vsecond, and third wp'ortions' ofsthe louverdefiningrringcooperating to'define a smoothly curved outer surface forreceiving air in a generally radial direction and then turning itsmoothly into an axial direction and discharging through said annularnozzle, the axial overlap 0 by which the louverdefining ring projectsinto the next adjacent liner section being on the order of one to twotimes h, the axial width of the louver inlet opening between the sharpannular corner and the adjacent edge of the second liner section beingon the order of two times h, the inner diameter of the outer housingbeing substantially constant and the upstream end of the second linersection being appreciably greater in diameter than the adjacent end ofthe first liner section, said upstream end of the second liner sectionhaving an outer surface tapering so that the extreme upstream endportion of the second liner section has a minimum outer diametersubstantially equal to that of the adjacent portion of the first linersection, whereby air flowing at high velocity in the supply spacebetween liner and housing flows past the entrance to said annular louverwith a minimum conversion of velocity head of the fluid in said supplypassage into static head at the entrance to the louver.

6. In a combustor having an outer housing containing an axiallyelongated liner defining a combustion chamber substantially closed atone end and formed of separate annular sections supported coaxiallywithin the outer housing and spaced therefrom to define an annularcombustion air supply passage with means for supplying air underpressure to said passage with a high velocity toward the discharge endof the liner, the combination of a first substantially cylindrical linersection having a discharge end portion cooperating with the adjacentupstream end portion of the next liner section to form an annular nozzlefor projecting a sheath of cooling and insulating fluid along the innersurface of said next adjacent section toward the discharge end thereof,said discharge edge portion of the first liner section having a smoothouter surface terminating at a substantially sharp annular corner, asecond portion projecting inwardly and having a substantially radialannular surface extending inwardly from said sharp corner, and a thirdannular nozzle portion extending axially and projecting in coaxialrelation with and spaced radially inward from the inner surface of thesecond liner section to define said annular nozzle, said first, second,and third portions of the first liner section cooperating to define asmoothly curved outer surface for receiving air radially and thenturning it smoothly into an axial direction and discharging through saidannular nozzle toward the discharge end of the second liner section, theadjacent edge of the second liner section being spaced axially from saidsharp annular corner to define an annular inlet opening for thesheathing air nozzle, the inner diameter of the outer housing beingsubstantially constant and the upstream end of the second liner sectionbeing appreciably greater in diameter than the adjacent end of the firstliner section, said end of the second section having an outer surfacetapering so that the extreme upstream end portion of the second sectionhas a minimum outer diameter substantially equal to that of the adjacentportion of the first liner section, whereby air flowing at high velocityin the annular supply space between liner and housing is maintained atsubstantially constant velocity for effective cooling of the outersurface of the liner with a minimum disturbance of said high velocityflow occasioned by the change in diameter of successive liner sectionsand with a minimum tendency for velocity head of the fluid in saidsupply passage to be converted into static head at the entrance to thesheathing fluid louvers.

References Cited in the file of this patent UNITED STATES PATENTS

